Add new resource for Kubernetes API proxy (#279)

This adds a new resource which deploys a Kubernetes API server proxy
that can be used to access the API server without tokens through
Netbird.

Part of #274 

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## Summary by CodeRabbit

* **New Features**
* Added ClusterProxy custom resource for cluster API proxying
capabilities

* **Documentation**
  * Added ClusterProxy API reference documentation with schema details

* **Examples**
* Added example ClusterProxy configuration and RBAC setup for cluster
proxy targets

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examples/api-proxy/api-proxy.yaml

@@ -0,0 +1,70 @@
+apiVersion: netbird.io/v1alpha1
+kind: ClusterProxy
+metadata:
+  name: prod
+  namespace: netbird
+spec:
+  clusterName: prod
+  serviceAccountName: clusterproxy-prod
+---
+apiVersion: v1
+kind: ServiceAccount
+metadata:
+  name: clusterproxy-prod
+  namespace: netbird
+---
+apiVersion: rbac.authorization.k8s.io/v1
+kind: ClusterRole
+metadata:
+  name: clusterproxy-prod
+rules:
+  - apiGroups:
+      - ""
+    resources:
+      - users
+      - groups
+    verbs:
+      - impersonate
+
+  - apiGroups:
+      - authentication.k8s.io
+    resources:
+      - userextras/*
+      - uids
+    verbs:
+      - impersonate
+---
+apiVersion: rbac.authorization.k8s.io/v1
+kind: ClusterRoleBinding
+metadata:
+  name: clusterproxy-prod
+roleRef:
+  apiGroup: rbac.authorization.k8s.io
+  kind: ClusterRole
+  name: clusterproxy-prod
+subjects:
+  - kind: ServiceAccount
+    name: clusterproxy-prod
+    namespace: netbird
+---
+apiVersion: rbac.authorization.k8s.io/v1
+kind: ClusterRole
+metadata:
+  name: netbird-cluster-reader
+rules:
+  - apiGroups: ["*"]
+    resources: ["*"]
+    verbs: ["get", "list", "watch"]
+---
+apiVersion: rbac.authorization.k8s.io/v1
+kind: ClusterRoleBinding
+metadata:
+  name: netbird-cluster-reader
+subjects:
+  - kind: Group
+    name: kubernetes-read
+    apiGroup: rbac.authorization.k8s.io
+roleRef:
+  kind: ClusterRole
+  name: netbird-cluster-reader
+  apiGroup: rbac.authorization.k8s.io